Cushioned hydraulic actuator

ABSTRACT

A hydraulic cylinder having a reciprocating piston and cushioning means on the end of the cylinder to decelerate the piston as it comes to the end of its stroke. The decelerating means includes a valving means and orifice means to restrict the flow and produce throttling of the hydraulic fluid as the piston nears the end of its stroke.

1 1 Apr. 15, 1975 CUSHIONED HYDRAULIC ACTUATOR [75] Inventor: Herbert Z.Langland, Topeka, Kans.

[73] Assignee: Allis-Chalmers Corporation,

Milwaukee, Wis.

22 Filed: Mar. 2, 1973 211 Appl. No.1 337,531

2,547,861 4/1951 Fletcher 91/406 X 2,783,742 3/1957 Shafer 91/407 X2,831,933 4/1958 Schrameck et al.. 91/406 X 3,039,485 6/1962 Brohl251/117 X 3,054,384 9/1962 Darling 91/26 X 3,162,092 12/1964 Corwin91/407 X 3/1967 Allen 137/5962 X Primary Examiner-Jrwin C. CohenAssistant ExaminerAbraham l-lershkovitz [52] US. Cl. 91/406; 91/24;91/31; Attorney, Agent, or Firm-Arthur L. Nelson 91/407; 92/143;137/596.2; 251/117 [51] Int. Cl. [58] Field of Search 91/404, 405, 406,407,

9l/25 26, 24, 31; 92/143; 251/l17 X; A hydraulic cylinder havmg areciprocating piston and 137/5962 X cushioning means on the end of thecylinder to decelerate the piston as it comes to the end of its stroke.[56] References Cited Th? decelerating metanstirtilclutdles availvingdmeantshantd on ice means 0 res me e ow an pro uce ro UNITEDSTATES PATENTS tling of the hydraulic fluid as the piston nears the end1,891,312 12/1932 Knecht 91/406 X of its Stroke 2,247,201 6/1941 Loos91/406 X 2,338,845 1/1944 Gunner et a1. 91/406 X 10 Claims, 3 DrawingFigures 37 27 Ill 28 U U r:: 1 Q I PATENIEB RPR 1 5 I975 SHEET 1 2FMENTEDAFR I SISYS saw 2 pg 2 CUSHIONED HYDRAULIC ACTUATOR Thisinvention relates to a hydraulic cylinder and more particularly to acushioning means to decelerate the movement of the piston as it nearsthe end of its stroke.

Hydraulic cylinders are used to perform a number of operations inhydraulic systems used on motor vehicles. 7

Most of the hydraulic cylinders carry a substantial load and duringtheir operation are subjected to inertia forces. This is particularlytrue of the hydraulic cylinder as it nears the end of its stroke. Theload carried by the hydraulic cylinder is often so great that if theload were allowed to force the piston unrestrained to the end of itsstroke in the hydraulic cylinder, it may cause irrepairable damage tothe cylinder. Shock loading of this type cannot be tolerated in thehydraulic system not only because it may damage the hydraulic cylinderbut the load itself may be subjected to excessive inertia forces.

Accordingly, this invention provides a means whereby inertia forcesnormally produced by the load on the hydraulic cylinder at the end ofthe piston stroke are substantially reduced or eliminated to preventdamage to the hydraulic cylinder and to provide smooth operation of thehydraulic system in handling the load carried by the hydraulic cylinder.The cushioning means in the hydraulic cylinder is accomplished throughthrottling of the hydraulic fluid as the piston nears the end of itsstroke. The throtting is produced by a valve which is actuated by thepiston to close a valve and force fluid through an orifice or a checkvalve to eliminate the shock and inertia forces suddenly imposed on thehydraulic cylinder as it reaches the end of its stroke.

It is an object of this invention to provide a cushioned hydrauliccylinder or hydraulic actuator for decelerating the movement of thepiston near the end of its stroke.

It is another object of this invention to provide a cushioned hydrauliccylinder for decelerating the movement of the piston near the end of itsstroke with a cushioning means in a removable cartridge to permitremoval of the cartridge for easy repair and servicing.

It is a further object of this invention to provide cushioning means ina hydraulic actuator for throttling the hydraulic fluid through aclosing poppet valve in the end of the hydraulic actuator, an orifice,and a check valve to prevent shock loading and high pressures in thehydraulic chamber as the piston nears the end of its stroke.

It is a further object of this invention to provide a cushionedhydraulic actuator to decelerate the piston movement as it nears the endof its stroke by throttling through a closing poppet valve, an orifice,and check valve and to limit high pressures and eliminate high inertiaforces as the piston comes to the end of its stroke.

The objects of this invention are accomplished by providing throttlingmeans in the end ofa hydraulic actuator which throttle the fluid as itis discharged from the hydraulic actuator near the end of the pistonstroke. The cushioning means includes a poppet valve and orifice in thehead of the hydraulic actuator which can be readily removed'forservicing and repair to keep the cushioning means in the best ofoperating conditions. Together with the poppet valve and an orifice, acheck valve is also provided to eliminate any shock or inertia forcesfrom damaging the end of the hydraulic actuator as the piston nears theend of its stroke and particularly when the hydraulic actuator is undera loaded condition.

The preferred embodiment of this invention is illustrated in theattached drawings.

FIG. 1 is a cross:sectin view which illustrates an hydraulic actuatorwith a cushioning means.

FIG. 2 is an enlarged cross-section view which illus trates a removablycartridge for operation as a cushioning means in the hydraulic actuatorof FIG. I with the poppet valve open.

FIG. 3is an enlarged cross-section view of the end of the hydraulicactuator shown in FIG. 1 with the poppet valve in closed position andthe piston near the end of its stroke.

) Referring to the drawings, FIG. 1 shows the hydraulic actuator incross section. The hydraulic actuator l includes a cylindrical housing 2encasing a piston 3 carrying the seals 4 and 5 and a ring 6 for sealingthe hydraulic fluid between the chambers 7 and 8. The piston 3 isconnected to a piston rod 9 by means of a bolt end 10 and nut 11. Thepiston rod extends through the end wall 12 which has a cylindricalopening 13 which receives the seals 14 and 15 to seal the chamber 7 ofthe external side of the hydraulic actuator.

The end wall 12 is also provided with a seal 16 on an external peripheryengaging the internal periphery of the cylindrical housing 2. The snapring 17 locks the assembly against an internal force and an external nut18 threadedly engages the end of the wall 12 to lock assembly againstthe cylindrical housing 2.

The cylindrical housing 2 is also fabricated to the trunnion bearings 19and 20. The trunnion bearing 19 includes the bearing shell 21 having anopening for receiving lubricant through the grease fitting 22. Thetrunnion bearing is also fitted with a bearing shell 23 and a similargrease fitting 24 for lubrication of the trunnion bearing 20. v

The piston rod 9 includes a bearing end 25 which receives the bushing 26which is adapted for connection to a shaft for carrying the externalload on the hydraulic actuator 1.

The hydraulic actuator 1 includes a head 27 which is welded at 28 to thecylindrical housing 2. The head 27 together with the piston 3 and thecylindrical housing 2 forms the expansible chamber 8. The head 27 alsoforms a valve chamber 29 which is in communication with the flow port 30adapted for connection to a source of fluid. The flow of fluid throughthe port 30 may be of high pressure to extend the piston and expand thechamber 8 or of a low pressure fluid when the fluid is discharged fromthe expansible chamber 8 through the poppet valve 31.

A check valve 32 is also contained within the head 27. The check valve32 is contained within the compartment 33 and includes the valve seat 34which has cross passages 35 for receiving fluid from the expansiblechamber 8. The valve seat 34 has a threaded portion 36 which threadedlyengages the valve support 37 which in turn has a threaded portion 38which threadedly engages a threaded opening 39 in the head 27. Asuitable seal 40 is provided underneath the head 41 of the valve support37. The valve support 37 carries the valve seat 34 and can be removed asa unit from the head 27 if servicing is desired. The check valve 32includes a ball 42 and spring 43 normally biasing the check valve to aclosed position. Suitable passages are provided to transmit fluid fromthe cross passages 35 in the valve seat 34 to the cross passages 44 inthe valve support 37 which provide communication between the expansiblechamber 8 and the compartment 33.

The check valve 32 is formed with a peripheral groove 70 to receive theseal 71 to seal the expansible chamber 8 from the valve chamber 29.

The poppet valve 31 includes the valve body 45 having a threaded portion46 which threadedly engages a threaded opening 47 in the head 27 and isremovable as a valve cartridge. The valve body 45 also is provided witha threaded interior 48 which threadedly receives the threaded portion 49of the cap 50. A seal 51 is received within the annular recess 52 toprovide a seal between the expansible chamber 8 and the valve chamber29. The seal 53 between the valve body 45 and the head 27 seals thechamber 29 from the exterior side of the head while the seal 54 providesa seal between the cavity 55 and the exterior side of the hydraulicactuator.

The spring seat 57 is seated within the cap 50 and has a stem 58received within the spring 59. The spring 59 is compressibly positionedbetween the spring seat 57 and the retainer ring 60. Similarly a spring61 is compressibly positioned between the retainer 60 and the snap ring62 carried on the plunger 63. The poppet 64 is slidably positionendwithin the valve body 45 and normally biased to the open position asshown in FIG. 2. The valve body 45 forms a valve seat 65 which engages aconical surface 66 when the poppet valve is in the closed position asshown in FIG. 3.

The poppet forms an orifice 67 providing communication between the valvechamber 29 and the expansible chamber 8 when the poppet valve 31 is inthe closed position.

The snap ring 68 provides a stop to limit the open position of thepoppet valve 31.

The operation of the cushioning means will be described in the followingparagraphs.

When the hydraulic actuator is in operation and the piston 3 is in aposition remote from the head 27, the poppet 64 is spring biasedoutwardly by the spring 59 compressed against the retaining ring 60which engages the inner periphery of valve body 45. The plunger 63 isspring biased outwardly by the spring 61 compressively positionedbetween the retaining rings 62 and 60. With the plunger and the poppetin the extended position oil can flow freely from the expansible chamber8 to the valve chamber 29.

As the piston moves near the end of its stroke it contacts the plunger63. The poppet 64 then becomes unbalanced due to the load induced by theplunger spring 61. As the poppet 64 moves toward the spring retainer 57the oil .in expansible chamber 8 assists the spring in forcing thepoppet 64 to seat on the valve seat 65 of the valve body 45 due to thepressure drop caused by a reduced outlet area in the poppet valve 32.After the poppet 64 has seated on the seat 65 oil can be exhaustedthrough the orifice 67 in the poppet 64 or through the relief valve 32.Normally the relief valve opens after the poppet has seated. Reliefvalve 32 then reseats. The remaining oil is forced through the orifice67. When the poppet seats on the seat 65 of the valve body 45 theplunger 63 will continue to retract through the remainder of the pistonstroke and the load against the springs 61 remains as the resilience ofthe spring allows for this overtravel. The piston stroke is such thatthe piston rod 9 stops short of the striking of the poppet 64.

To extend the piston rod 9 and the piston 3 in the hydraulic actuatorhydraulic fluid flows through the flow port 30 into the valve chamber 29opening the poppet valve 31 and flowing into the expansible chamber 8.The oil pressure unseats the poppet valve 31 expanding the plungersprings 61 as the oil enters the expansible chamber 8 through the valve.As the piston rod moves with the piston 3 the piston 3 moves out untilthe retaining ring 62 engages the radical flange 73 of the poppet 64. Asthe piston 3 and rod 9 move to the extended position within thehydraulic actuator the poppet 64 of the poppet valve 31 fully opens withsnap ring 68 engaging surface of valve body 45. The plunger 63 withinthe poppet 64 extends to its fully extended position and fluid flowsfreely through the flow port 30, the valve chamber 29 and the poppetvalve 31 into the expansible chamber 8.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A hydraulic actuator comprising a cylindrical housing, a headfastened to the end of said cylindrical housing defining a valve chambercommunicating with a flow port, a piston slidably received within saidcylindrical housing and forming an expansible chamber with said head, aremovable valve cartridge mounted in said head including a valve bodydefining a valve seat, a valve element slidably mounted within saidvalve body and defining a poppet valve with said valve seat in saidbody, fastening means on said head and valve cartridge removablyfastening said valve cartridge in said valve chamber said valvecartridge controlling fluid flow between said expansible chamber andsaid valve chamber conduit means through said valve body interconnectingthe internal and external portions thereof, means defining an orificeproviding restrictive fluid passage across said poppet valve andcommunicating said expansible chamber with said valve chamber via saidconduit means, a relief valve, means supporting said relief valve insaid head and passage means within said head communicating saidexpansible chamber with said relief valve and further passage meanswithin said head communicating said relief valve with said valve chamberto limit peak pressures in said expansible chamber, resilient meansinterposed between said valve body and said valve element normallybiasing said valve element to an open position, a valve actuatingplunger, resilient means interposed between said valve element andsaidplunger, said plunger engaging said piston to close said poppetvalve and provide restrictive fluid flow through said orifice when saidpiston nears the end of its stroke and thereby cushioning the movementof the piston by restricting the flow of fluid from said expansiblechamber.

2. A hydraulic actuator as set forth in claim 1 including, a reliefvalve casing housing said relief valve and fastening means removablysupporting said relief valve casing in said head.

3. A hydraulic actuator as set forth in claim 1 wherein said reliefvalve defines a ball check valve,

means removably fastening said relief valve in said head, said reliefvalve providing relief of peak pressures in said expansible chamber whensaid piston nears the end of its stroke.

4. A hydraulic actuator as set forth in claim 1 wherein said valveelement defines said orifice.

5. A hydraulic actuator as set forth in claim 1 including a springnormally biasing said plunger to an extended position for engaging saidpiston when said piston nears the end of its stroke.

6. A hydraulic actuator as set forth in claim 1 wherein said valveactuating plunger defines a hollow plunger, means defining a centralopening in said valve element for reciprocally receiving said plunger,ports means in said plunger for transmitting fluid from said centralopening in said valve element when said plunger is biased by said pistonto close said valve.

7. A hydraulic actuator as set forth in claim 1 where said fasteningmeans, includes said valve body defining a cylindrical sleeve includinga threaded portion, and means defining a cylindrical opening in saidhead having a threaded portion for receiving said cylindrical sleeve.

8. A hydraulic actuator as set forth in claim 1 including said reliefvalve positioned in said head to permit fluid flow only from saidexpansible chamber to said valve chamber to limit peak pressures in saidexpansible chamber when said piston nears the end of its stroke.

9. A hydraulic actuator as set forth in claim 1, said head includingmeans centrally supporting said valve cartridge in said hydraulicactuator.

10. A hydraulic actuator as set forth in claim 1 wherein said valve bodydefines a sleeve, said valve element defines said poppet valve mountedwithin said sleeve, said poppet valve defines said orifice whereby saidorifice and said poppet valve control the flow to and from saidexpansible chamber in said hydraulic actuator.

1. A hydraulic actuator comprising a cylindrical housing, a headfastened to the end of said cylindrical housing defining a valve chambercommunicating with a flow port, a piston slidably received within saidcylindrical housing and forming an expansible chamber with said head, aremovable valve cartridge mounted in said head including a valve bodydefining a valve seat, a valve element slidably mounted within saidvalve body and defining a poppet valve with said valve seat in saidbody, fastening means on said head and valve cartridge removablyfastening said valve cartridge in said valve chamber said valvecartridge controlling fluid flow between said expansible chamber andsaid valve chamber conduit means through said valve body interconnectingthe internal and external portions thereof, means defining an orificeproviding restrictive fluid passage across said poppet valve andcommunicating said expansible chamber with said valve chamber via saidconduit means, a relief valve, means supporting said relief valve insaid head and passage means within said head communicating saidexpansible chamber with said relief valve and further passage meanswithin said head communicating said relief valve with said valve chamberto limit peak pressures in said expansible chamber, resilient meansinterposed between said valve body and said valve element normallybiasing said valve element to an open position, a valve actuatingplunger, resilient means interposed between said valve element and saidplunger, said plunger engaging said piston to close said poppet valveand provide restrictive fluid flow through said orifice when said pistonnears the end of its stroke and thereby cushioning the movement of thepiston by restricting the flow of fluid from said expansible chamber. 2.A hydraulic actuator as set forth in claim 1 including, a relief valvecasing housing said relief valve and fastening means removablysupporting said relief valve casing in said head.
 3. A hydraulicactuator as set forth in claim 1 wherein said relief valve defines aball check valve, means removably fastening said relief valve in saidhead, said relief valve providing relief of peak pressures in saidexpansible chamber when said piston nears the end of its stroke.
 4. Ahydraulic actuator as set forth in claim 1 wherein said valve elementdefines said orifice.
 5. A hydraulic actuator as set forth in claim 1including a spring normally biasing said plunger to an extended positionfor engaging said piston when said piston nears the end of its stroke.6. A hydraulic actuator as set forth in claim 1 wherein said valveactuating plunger defines a hollow plunger, means defining a centralopening in said valve element for reciprocally receiving said plunger,ports means in said plunger for transmitting fluid from said centralopening in said valve element when said plunger is biased by said pistonto close said valve.
 7. A hydraulic actuator as set forth in claim 1where said fastening means, includes said valve body defining acylindrical sleeve including a threaded portion, and means defining acylindrical opening in said head having a threaded portion for receivingsaid cylindrical sleeve.
 8. A hydraulic actuator as set forth in claim 1including said relief valve positioned in said head to permit fluid flowonly from said expansible chamber to said valve chamber to limit peakpressures in said expansible chamber when said piston nears the end ofits stroke.
 9. A hydraulic actuator as set forth in claim 1, said headincluding means centrally suppOrting said valve cartridge in saidhydraulic actuator.
 10. A hydraulic actuator as set forth in claim 1wherein said valve body defines a sleeve, said valve element definessaid poppet valve mounted within said sleeve, said poppet valve definessaid orifice whereby said orifice and said poppet valve control the flowto and from said expansible chamber in said hydraulic actuator.